<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script type="text/javascript">
    setTimeout(() => {
      console.log("0")
    }, 0)
    new Promise((resolve, reject) => {
      console.log("1")
      resolve()
    }).then(() => {
      console.log("2")
      new Promise((resolve, reject) => {
        console.log("3")
        resolve()
      }).then(() => {
        console.log("4")
      }).then(() => {
        console.log("5")
      })
    }).then(() => {
      console.log("6")
    })

    new Promise((resolve, reject) => {
      console.log("7")
      resolve()
    }).then(() => {
      console.log("8")
    })
  </script>

</body>

</html>